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Interstage Echocardiographic Changes in Patients Undergoing Hybrid Stage I Palliation for Hypoplastic Left Heart Syndrome
Interstage Echocardiographic Changes in Patients Undergoing Hybrid Stage I Palliation for Hypoplastic Left Heart Syndrome Bernadette Fenstermaker, RDCS, Glen E. Berger, RDCS, Daniel G. Rowland, MD, John Hayes, PhD, Sharon L. Hill, ACNP, John P. Cheatham, MD, Mark Galantowicz, MD, and Clifford L. Cua, MD, Columbus, Ohio
Objective: The hybrid procedure is an alternative for initial palliation for patients with hypoplastic left heart syndrome. No echocardiographic data exist for the interstage (IS) period. The goal of this study was to describe the echocardiographic changes during this period. Methods: A chart review was performed on patients discharged from the hospital with the diagnosis of hypoplastic left heart syndrome who underwent hybrid palliation. Echocardiograms at hospital discharge (post-hybrid), before and after any IS interventions, and before comprehensive stage II procedure were reviewed. Distal right pulmonary artery (RPA) and left pulmonary artery (LPA) velocity, slope, velocity time integral (VTI), pressure halftime (p1/2), pulsatility index (PI), and systolic/diastolic (S/D) ratio of the waveforms were recorded. Atrial septal defect (ASD) mean gradient, ductus arteriosus peak velocity, retro-aortic arch peak velocity, tricuspid regurgitation (TR), and right ventricular function were documented. Exploratory hypotheses were tested with chi-square and t tests. Stepwise logistic regression was used to identify any multiple sets of relatively independent variables. Results: Thirty patients met inclusion criteria. Fourteen patients underwent 22 different interventions at the atrial septum, ductus arteriosus, or retro-aortic arch in the IS period. Baseline ASD gradient (P ⫽ .012) and ductus arteriosus velocity (P ⫽ .002) predicted an IS intervention. There were significant differences in LPA and RPA VTI (P ⫽ .011, .03), p1/2 (P ⫽ .038, .008), and S/D (P ⫽ .012, .033); RPA slope (P ⫽ .013); ASD gradient (P ⫽ .003); ductus arteriosus velocity (P ⫽ .021); and TR (P ⫽ .031) before and after an intervention. There were significant differences in post-hybrid versus pre-comprehensive stage II LPA and RPA VTI (P ⫽ .009, .022), PI (P ⫽ .031, .022), and peak velocity (P ⫽ .004, .037); RPA S/D (P ⫽ .025) and p1/2 (P ⫽ .029); ductus arteriosus velocity (P ⬍ .001); retro-aortic arch peak velocity (P ⫽ .035); and ASD mean gradient (P ⬍ .001). Pre-comprehensive stage II function tended to predict death (P ⫽ .085). Conclusion: Echocardiographic parameters help predict IS course and guide clinical therapy for this patient population. (J Am Soc Echocardiogr 2008;21:1222-1228.) Keywords: Catheterization, Congenital heart disease, Cyanotic heart disease, Echocardiography, Hypoplastic left heart
Hybrid palliation consisting of bilateral pulmonary artery bands, stenting of the ductus arteriosus, and balloon atrial septostomy has become another alternative for treatment of patients with hypoplastic left heart syndrome (HLHS).1,2 Initial reports have documented similar results with the hybrid procedure compared with more
From The Heart Center (B.F., G.E.B., D.G.R., J.H., S.L.H., J.P.C., M.G., C.L.C.), Division of Pediatrics (D.G.R., J.P.C., C.L.C.), and Cardiothoracic Surgery (M.G.), The Ohio State University and Nationwide Children’s Hospital, Columbus, Ohio. Presented at: Update on Pediatric Cardiovascular Disease February 6-10, 2008, Scottsdale, AZ. Reprint requests: Clifford Cua, MD, Columbus Children’s Hospital, 700 Children’s Drive, Columbus, OH 43205-2696 (E-mail: [email protected]). 0894-7317/$34.00 Copyright 2008 by the American Society of Echocardiography. doi:10.1016/j.echo.2008.08.005
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traditional surgical options.2,3 Although the physiology is different, the goals of the palliation are the same as the traditional surgical palliation, which are to control pulmonary blood flow, provide reliable systemic cardiac output, and create an unrestrictive interatrial communication. After the comprehensive stage II surgery, which consists of pulmonary artery debanding, stent removal, arch augmentation with anastomosis of the main pulmonary artery to the ascending aorta, atrial septectomy, and bidirectional Glenn anastomosis, the physiology of patients undergoing the hybrid palliation is equivalent to those who have undergone a more traditional pathway through the bidirectional Glenn procedure (anastomosis of the superior vena cava to the pulmonary artery). Although echocardiographic findings have been described for patients who have undergone the classic Norwood procedure4-6 (atrial septectomy, anastomosis of the main pulmonary artery to the ascending aorta, aortic arch augmentation, and placement of a shunt from the innominate artery to the right pulmonary artery [RPA] to
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supply pulmonary blood flow) or the modified Norwood procedure7 (pulmonary blood flow supplied via a right ventricular to pulmonary artery conduit instead of a shunt), and subsequently the bidirectional Glenn operation8,9 and Fontan procedure10,11 (anastomosis of the inferior vena cava to the pulmonary artery), no data exist for those undergoing hybrid palliation. There are different physiologic issues that must be followed echocardiographically for patients undergoing the hybrid palliation versus those who undergo a more traditional pathway. The goal of this study was to describe the echocardiographic changes during the interstage (IS) period, defined as the time from hospital discharge after hybrid palliation to hospitalization for the comprehensive stage II operation, and to determine whether certain echocardiographic parameters may predict morbidity and mortality. MATERIALS AND METHODS Patient Selection This study was approved by the Institutional Review Board of Nationwide Children’s Hospital. Inclusion criteria included patients with HLHS, defined as aortic atresia/mitral atresia, aortic atresia/ mitral stenosis, or aortic stenosis/mitral stenosis, who underwent hybrid palliation and were discharged from the hospital. Patients were excluded if they (1) had an anatomic diagnosis different from those stated above, (2) were followed at another institution during the IS period, or (3) had not undergone their comprehensive stage II operation at the time of the analysis. A retrospective chart review was performed on all patients who met the inclusion criteria. Baseline data consisting of anatomic diagnosis, gender, age, and weight at the time of the hybrid procedure were recorded. Interventional procedures performed before the hybrid procedure and any additional IS cardiac procedures were documented. The age and weight of the patient at the comprehensive stage II were also recorded. Echocardiography All cardiac ultrasound examinations were performed at the Nationwide Children’s Hospital as part of routine clinical care. Examinations included standard transthoracic 2-dimensional echocardiography and pulsed, continuous wave, and color Doppler using variable frequency transducers. The studies were performed using various ultrasound systems (Sonos 5500 and iE33, Philips Medical Systems, Andover, MA; Vivid 7, GE Medical, Milwaukee, WI; Sequoia C256, Siemens, Mountain View, CA). Echocardiograms post-hybrid palliation before hospital discharge, before and after an IS intervention, and before the comprehensive stage II procedure were reviewed. The echocardiograms evaluated post-hybrid palliation were usually within 2 to 3 weeks after the procedure, and the pre-comprehensive stage II was also within 2 to 3 weeks before the operation. Offline analysis of the distal RPA and left pulmonary artery (LPA) (Figure 1) peak velocities (m/s), slope (cm/s2), VTI (cm), pressure halftime (P1/2) (ms), PI (peak systolic velocity-diastolic velocity)/mean velocity, and systolic/diastolic (S/D) ratio of the waveforms were recorded (Figure 2) in the parasternal short-axis view. ASD mean gradient (mm Hg) in the subcostal view (Figure 3), ductus arteriosus peak velocity (m/s) (Figure 4), and retro-aortic arch peak velocity (m/s) (Figure 5) in the high parasternal view were documented. The highest velocity or gradient that was imaged was recorded. Qualitative assessment of TR and right ventricular function was also documented. TR was graded as severe if there was systolic flow reversal in the inferior vena cava or hepatic vein, moderate if there
Figure 1 High parasternal short-axis view of the typical branch pulmonary arteries and ductal stent image. LPA, Left pulmonary artery; MPA, main pulmonary artery; PDA, patent ductus arteriosus; RPA, right pulmonary artery.
Figure 2 Typical Doppler pattern of the branch pulmonary artery velocity wave form and the various measurements performed. PHT, Pressure halftime; VTI, velocity time integral. was right atrial enlargement without flow reversal, mild if there was a regurgitant jet present without right atrial dilation, and trace/none if there was trivial or no jet present. Regurgitation and function were graded as 1 ⫽ normal/trace, 2 ⫽ mild, 3 ⫽ moderate, and 4 ⫽ severe for statistical purposes. Statistical Analysis The data are described with means, standard deviations, and percentages. Exploratory hypotheses were tested with chi-square and t tests. Stepwise logistic regression was used to identify any multiple sets of relatively independent variables. RESULTS Study Population Between July of 2002 and December of 2006, 35 patients with the diagnosis of HLHS underwent hybrid palliation and were discharged
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Figure 3 Subcostal view of the atrial septum documenting aliasing across the defect. Doppler interrogation would be performed in this view to obtain the mean gradient across the septum. from the hospital. Two patients were followed at another institution, and 3 patients were awaiting their comprehensive stage II procedure. Therefore, the cohort for this study consists of 30 patients. The age at hybrid palliation was 11.3 ⫾ 15.8 days (median 8 days, range 2-15 days), with 1 patient undergoing the hybrid palliation at 93 days as a rescue procedure. The weight was 3.0 ⫾ 0.6 kg (median 3.0 kg, range 1.4-4.5 kg). Four patients weighed less than 2.5 kg at the time of the hybrid palliation. Twenty-four (80%) of the patients were male. Sixteen patients (53%) had aortic atresia/mitral atresia, 4 patients (13%) had aortic atresia/mitral stenosis, and 10 patients (33%) had aortic stenosis/mitral stenosis. Four patients had a highly restrictive ASD that required urgent balloon atrial septostomy before undergoing hybrid palliation. Fourteen patients (47%) underwent a total of 18 separate cardiac catheterization procedures with a total of 22 interventions performed at the atrial septum, ductus arteriosus, or distal aortic arch during the IS period. Six additional stents were placed in the ductus arteriosus, 7 repeat balloon atrial septostomies were performed, 3 dilations of the ductus arteriosus stent were performed, 3 stents were placed in the distal arch, 1 stent was placed in the atrial septum, 1 dilation of the descending aorta was performed, and 1 dilation of the left pulmonary vein was performed. Two patients required reoperation: one for progressive pulmonary vein stenosis and one for a loose pulmonary artery band. There were 2 IS deaths. The weight at the comprehensive stage II procedure was 5.6 ⫾ 1.1 kg, and the age was 167.4 ⫾ 60.8 days.
Figure 4 (A) High parasternal image where highest velocity is usually obtained across the ductus arteriosus stent. (B) Continuous wave Doppler across a stenotic ductus arteriosus stent. CW, Continuous wave; PDA, patent ductus arteriosus.
Echocardiographic Data By comparing the post-hybrid echocardiogram with the pre-comprehensive stage II echocardiogram in the patients who did not undergo any IS intervention, there were significant differences in a number of the Doppler variables (Table 1). Significant interval changes in the flow characteristics in the LPA and RPA, with increases in the peak velocities, VTI, P1/2, and S/D ratios, and a decrease in PI, were documented. The LPA and RPA slope, however, did not change significantly. There were significant increases in the ductus arteriosus velocity, ASD mean gradient, and retro-aortic arch peak velocity during this time period.
When examining the echocardiographic data on the subset of patients who underwent an IS intervention (Table 2), there were similar increases in the LPA and RPA peak velocities and VTI, ductus arteriosus flow velocity, and retro-aortic arch peak velocity. In addition, there were significant changes in the ASD gradient, LPA slope, degree of TR, and right ventricular function between the post-hybrid echocardiogram and the echocardiogram before the intervention. By analyzing each of the different interventions separately, there were no significant differences in any of the parameters between the post-hybrid and pre-intervention echocardiograms at the distal aortic
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Table 1 Post-hybrid echocardiogram versus pre-comprehensive stage II procedure echocardiogram in patients who had no interstage intervention Post-hybrid echocardiogram
LPA velocity (m/s) RPA velocity (m/s) LPA VTI (cm) RPA VTI (cm) RPA p1/2 (ms) LPA PI RPA PI RPA S/D ASD gradient (mm Hg) DA velocity (m/s) Retro-aortic arch (m/s)
3.58 3.54 98.04 103.43 121.44 1.12 1.03 3.60 1.39 1.61 1.71
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.80 0.81 32.12 32.05 26.32 0.20 0.32 1.90 1.08 0.47 0.67
Pre-stage II echocardiogram
4.38 4.06 137.15 131.49 142.48 0.92 0.79 2.33 3.21 2.82 2.56
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.59 0.44 36.31 27.60 24.51 0.32 0.18 0.44 2.35 0.44 1.02
P
.004 .037 .009 .022 .029 .031 .022 .025 .029 ⬍.001 .035
ASD, Atrial septal defect; LPA, left pulmonary artery; NS, not significant; DA, ductus arteriosus; PI, pulsatility index; RPA, right pulmonary artery; VTI, velocity time integral; p1/2, pressure halftime.
Table 2 Post-hybrid echocardiogram versus pre-intervention echocardiogram Post-hybrid echocardiogram
LPA velocity (m/s) RPA velocity (m/s) LPA slope (cm/s2) RPA slope (cm/s2) LPA VTI (cm) RPA VTI (cm) LPA p1/2 (ms) RPA p1/2 (ms) LPA S/D RPA S/D LPA PI RPA PI ASD gradient (mm Hg) DA velocity (m/s) Retro-aortic arch (m/s) TR RV function
3.48 3.44 920.10 866.01 90.80 99.07 107.29 115.95 3.85 3.24 1.09 1.00 2.14 1.84 1.76 1.22 1.06
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
Pre-intervention echocardiogram
P
0.71 3.97 ⫾ 0.82 .005 0.66 3.89 ⫾ 0.62 .008 298.74 1081.22 ⫾ 405.55 .041 216.12 975.36 ⫾ 340.29 NS 28.43 115.07 ⫾ 41.78 .002 24.02 117.56 ⫾ 36.11 .015 25.11 118.11 ⫾ 43.65 NS 22.44 125.91 ⫾ 37.56 NS 2.10 3.60 ⫾ 1.94 NS 1.35 3.39 ⫾ 2.15 NS 0.21 1.11 ⫾ 0.27 NS 0.17 1.11 ⫾ 0.33 NS 1.52 4.91 ⫾ 4.33 .001 0.44 2.76 ⫾ 0.57 ⬍.001 0.47 2.34 ⫾ 0.81 .002 0.49 1.61 ⫾ 0.90 .017 0.23 1.30 ⫾ 0.76 .02
ASD, Atrial septal defect; LPA, left pulmonary artery; NS, not significant, DA, ductus arteriosus; PI, pulsatility index; RPA, right pulmonary artery; RV, right ventricle; TR, tricuspid regurgitation; VTI, velocity time integral; p1/2, pressure halftime.
Figure 5 (A) High parasternal image where the retro-coarctation is best visualized. (B) Continuous wave Doppler across a stenotic retrograde aorta. CW, Continuous wave; PDA, patent ductus arteriosus.
arch, although there was a trend for increased TR (1.50 ⫾ 0.58 vs 3.00 ⫾ 0.82, P ⫽ .058). There was a significant increase in ductus arteriosus velocity on the echocardiograms for those undergoing a ductus arteriosus intervention (1.98 ⫾ 0.29 m/s vs 2.95 ⫾ 0.69 m/s, P ⫽ .003). There was a significant increase in the RPA slope (857.18 ⫾ 250.85 cm/s2 vs 1134.95 ⫾ 317.95 cm/s2, P ⫽ .044), but not in the LPA slope (933.411 ⫾ 276.18 cm/s2 vs 1106.71 ⫾ 322.24 cm/s2, P ⫽ .25), for those undergoing an intervention at the atrial septum. The ASD gradient (2.74 ⫾ 1.69 mm Hg vs 10.13 ⫾ 4.93 mm Hg,
P ⫽ .005) and TR (1.00 ⫾ 0.00 vs 1.71 ⫾ 0.76, P ⫽ .047) also significantly increased for these patients. There were significant differences in LPA and RPA VTI, p1/2, and S/D, and RPA slope, ASD gradient, ductus arteriosus gradient, and TR pre- and post-intervention (Table 3) for those requiring a procedure. A post-hybrid echocardiogram ASD mean gradient (P ⫽ .012) greater than 4.9 mm Hg or a ductus arteriosus peak velocity (P ⫽ .002) greater than 1.7 m/s predicted an IS intervention. However, there was no specific echocardiographic parameter that predicted a specific catheterization intervention. No echocardiographic parameter predicted comprehensive stage II mortality, although right ventricular function tended to predict death (P ⫽ .085).
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Table 3 Pre-intervention echocardiogram versus post-intervention echocardiogram Pre-intervention
LPA velocity (m/s) RPA velocity (m/s) LPA slope (cm/s2) RPA slope (cm/s2) LPA VTI (cm) RPA VTI (cm) LPA p1/2 (ms) RPA p1/2 (ms) LPA S/D RPA S/D LPA PI RPA PI ASD gradient (mm Hg) DA velocity (m/s) Retro-aortic arch (m/s) TR RV function
3.79 3.75 1152.84 1099.01 103.89 95.28 105.76 110.76 3.82 4.28 1.11 1.14 6.82 2.71 2.20 1.89 1.45
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.81 0.74 440.51 405.45 37.05 16.72 36.54 39.70 1.71 2.64 0.33 0.33 5.41 0.66 0.65 0.94 0.89
Post-intervention
P
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
NS NS NS .013 .011 .03 .038 .008 .012 .033 NS NS .003 .021 NS .031 NS
4.10 3.72 975.72 852.79 128.32 116.83 124.89 136.00 3.06 3.04 1.04 1.07 1.11 2.37 2.23 1.53 1.15
0.86 0.69 212.26 246.81 41.63 30.10 26.50 39.14 0.74 1.29 0.22 0.43 0.33 0.62 0.77 0.70 0.37
ASD, Atrial septal defect; LPA, left pulmonary artery; NS, not significant; DA, ductus arteriosus; PI, pulsatility index; RPA, right pulmonary artery; RV, right ventricle; TR, tricuspid regurgitation; VTI, velocity time integral; p1/2, pressure halftime.
DISCUSSION Hybrid palliation for newborns with HLHS is a relatively new technique for this population. The surgical and catheterization techniques have been described,1,2 but echocardiographic data have not been previously presented. Specifically, the echocardiographic parameters during the IS period, when the physiology of patients undergoing this procedure is different in comparison with those undergoing a classic or modified Norwood procedure, have not been previously delineated. This study shows that specific echocardiographic parameters change in a predictable manner during this time period and that variations from these changes may determine the clinical course. The post-hybrid echocardiogram ASD mean gradient and peak ductus arteriosus velocity were useful in predicting whether a patient would later require an IS intervention. No specific echocardiographic parameter predicted a certain catheterization procedure, but this may be because some patients had multiple procedures performed at a single catheterization. We no longer routinely perform a pre-comprehensive stage II catheterization, so the decision to perform an interventional catheterization is based on both clinical and echocardiographic data.2 Repeat balloon septostomy was performed if the echocardiographic mean gradient was 8 mm Hg or greater. The decision to intervene at the ductal or arch level is more complicated. Interventions at the ductal or arch level were performed if there were increasing gradients in these areas and worsening TR or right ventricular function. Clinical aspects, such as patient’s feeding pattern, weight gain, and electrocardiogram changes, also affected the decision to perform an intervention at the duct/arch. The complex changes in physiology with multiple procedures performed and the various clinical parameters used to guide the decision to intervene would make exact predictions difficult from the post-hybrid echocardiogram. Changes among the post-hybrid echocardiogram, pre-intervention echocardiogram, and post-intervention echocardiogram can be explained by changes in resistance distal to the pulmonary artery bands or increasing afterload. Restriction of flow across the atrial septum
Figure 6 (A) RPA Doppler interrogation in a patient with a restrictive atrial septum. Doppler pattern shows steep slope and low diastolic velocity. (B) RPA Doppler pattern after atrial balloon septostomy in the same patient. Notice the increase in diastolic velocity. Subsequent measurements documented increase in VTI, decrease in slope parameter, increase in pressure halftime, and decrease in S/D ratio. RPA, Right pulmonary artery; ¡, loss of forward during diastole; S/D, systolic/diastolic velocity.
and pulmonary vein obstruction can both result in increased diastolic pressures and thus decreased pulmonary blood flow. As a result, Doppler velocities across the bands will equilibrate quicker, as evidenced by the steeper slope seen in the pulmonary arteries. Although not statistically significant, a decrease in the systolic and diastolic velocities and an increase in PI have been noted as the ASD gradient increases. In severe restriction, diastolic flow across the bands can become minimal or nonexistent. When the restriction has been relieved, the pulmonary blood flow improves, the diastolic blood pressures decrease distal to the pulmonary artery bands, and the slope of the pulmonary waveforms becomes less steep and the PI decreases (Figure 6).
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Similarly, increasing afterload, either in the form of increasing stenosis across the ductal stent or retro-aortic arch, would result in decreased coronary perfusion, especially in patients with aortic atresia and thus no antegrade aortic flow. Coronary hypoperfusion would result in ventricular dysfunction, ventricular dilation, and TR. A stenotic ductus arteriosus stent will also increase systolic and diastolic ventricular pressures resulting from increased afterload and secondary hypertrophy of the single ventricle. This is consistent with the findings that TR and right ventricular dysfunction qualitatively increased compared with the hospital discharge study in patients requiring an intervention. Conversely, when the obstruction was relieved, the echocardiographic parameters postintervention corresponded to the values just before the comprehensive stage II procedure. Again, qualitatively, TR and ventricular function improved post-intervention. A more rapid or greater change in ductus arteriosus or retro-aortic arch flow velocities may signal intimal in-growth through the cells of the ductus arteriosus stent. In some cases this may be difficult to discern from the typical increases seen with growth, and clinical correlation is essential to determine further treatment plans. The echocardiogram before the comprehensive stage II procedure also was not predictive of mortality, although decreased right ventricular function tended to predict death. The lack of predictive power may be due to the small numbers studied, but it may also be due to the qualitative manner of grading right ventricular function. Because of the complex geometry of the right ventricle, no universal quantitative echocardiographic parameter has been agreed on. Newer techniques, such as 3-dimensional echocardiography, tissue Doppler velocities, strain, or strain rate, may be more sensitive markers for right ventricular function and thus be more predictive for clinical course.12-14 The echocardiographic changes seen between the post-hybrid and pre-comprehensive stage II procedure are likely due to multiple factors, including patient growth, fixed dimensions of anatomic structures such as the pulmonary artery bands and ductus arteriosus stent, and decreasing pulmonary vascular resistance. All 3 factors can explain the increases in peak pulmonary artery velocities and VTI measurements across the pulmonary artery bands and the decrease in PI. The increase in ductus arteriosus velocity can also be attributed to the fixed nature of the ductus arteriosus stent in the setting of a growing infant. Even patients who did not undergo an intervention had significant changes in parameters, and this may be the natural history as described above; thus, post-hybrid values cannot be considered a stagnant value. Although not examined in this study, growth appears to change the orientation of the distal arch in relation to the ductus, resulting in a more acute takeoff and altered flow dynamics resulting in more flow acceleration over time.15,16
LIMITATIONS The limitations of this study include its retrospective nature and the small numbers studied, although it is the largest study to date examining echocardiographic parameters in this complex patient population. Right ventricular function was qualitatively graded, so although it tended to predict comprehensive stage II mortality, no quantitative measurement at this time is available to predict death. Patients may also have had multiple interventions performed at a single cardiac catheterization, so complex physiologic interactions may not be totally explained by the pre- and post-echocardiographic findings.
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CONCLUSIONS Consistent and predictable changes in Doppler parameters were observed in patients with HLHS after hybrid palliation. Careful monitoring of these echocardiographic parameters with clinical correlation can help predict the IS course and the need for interventional therapy for this patient population. Close attention to changes in TR and right ventricular function is warranted. Further studies are needed to determine whether newer echocardiographic modalities of ventricular systolic and diastolic function may be more useful in identifying potential hemodynamic issues earlier and alter IS management and outcome for this patient population.
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13. Friedberg MK, Silverman NH. The systolic to diastolic duration ratio in children with hypoplastic left heart syndrome: a novel Doppler index of right ventricular function. J Am Soc Echocardiogr 2007;20:749-55. 14. Christensen D, Cardis B, Mahle W, Lewis R, Huckaby J, Favaloro-Sabatier J, et al. Pre- and postoperative quantitation of right ventricular tissue Doppler velocities in infants with hypoplastic left heart syndrome. Echocardiography 2006;23:303-7.
15. Boucek MM, Mashburn C, Kunz E, Chan KC. Ductal anatomy: a determinant of successful stenting in hypoplastic left heart syndrome. Pediatr Cardiol 2005;26:200-5. 16. Lemler MS, Zellers TM, Harris KA, Ramaciotti C. Coarctation index: identification of recurrent coarctation in infants with hypoplastic left heart syndrome after the Norwood procedure. Am J Cardiol 2000; 86:697-9, A9.
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Objective: The hybrid procedure is an alternative for initial palliation for patients with hypoplastic left heart syndrome. No echocardiographic data exist for the interstage (IS) period. The goal of this study was to describe the echocardiographic changes during this period. Methods: A chart review was performed on patients discharged from the hospital with the diagnosis of hypoplastic left heart syndrome who underwent hybrid palliation. Echocardiograms at hospital discharge (post-hybrid), before and after any IS interventions, and before comprehensive stage II procedure were reviewed. Distal right pulmonary artery (RPA) and left pulmonary artery (LPA) velocity, slope, velocity time integral (VTI), pressure halftime (p1/2), pulsatility index (PI), and systolic/diastolic (S/D) ratio of the waveforms were recorded. Atrial septal defect (ASD) mean gradient, ductus arteriosus peak velocity, retro-aortic arch peak velocity, tricuspid regurgitation (TR), and right ventricular function were documented. Exploratory hypotheses were tested with chi-square and t tests. Stepwise logistic regression was used to identify any multiple sets of relatively independent variables. Results: Thirty patients met inclusion criteria. Fourteen patients underwent 22 different interventions at the atrial septum, ductus arteriosus, or retro-aortic arch in the IS period. Baseline ASD gradient (P ⫽ .012) and ductus arteriosus velocity (P ⫽ .002) predicted an IS intervention. There were significant differences in LPA and RPA VTI (P ⫽ .011, .03), p1/2 (P ⫽ .038, .008), and S/D (P ⫽ .012, .033); RPA slope (P ⫽ .013); ASD gradient (P ⫽ .003); ductus arteriosus velocity (P ⫽ .021); and TR (P ⫽ .031) before and after an intervention. There were significant differences in post-hybrid versus pre-comprehensive stage II LPA and RPA VTI (P ⫽ .009, .022), PI (P ⫽ .031, .022), and peak velocity (P ⫽ .004, .037); RPA S/D (P ⫽ .025) and p1/2 (P ⫽ .029); ductus arteriosus velocity (P ⬍ .001); retro-aortic arch peak velocity (P ⫽ .035); and ASD mean gradient (P ⬍ .001). Pre-comprehensive stage II function tended to predict death (P ⫽ .085). Conclusion: Echocardiographic parameters help predict IS course and guide clinical therapy for this patient population. (J Am Soc Echocardiogr 2008;21:1222-1228.) Keywords: Catheterization, Congenital heart disease, Cyanotic heart disease, Echocardiography, Hypoplastic left heart
Hybrid palliation consisting of bilateral pulmonary artery bands, stenting of the ductus arteriosus, and balloon atrial septostomy has become another alternative for treatment of patients with hypoplastic left heart syndrome (HLHS).1,2 Initial reports have documented similar results with the hybrid procedure compared with more
From The Heart Center (B.F., G.E.B., D.G.R., J.H., S.L.H., J.P.C., M.G., C.L.C.), Division of Pediatrics (D.G.R., J.P.C., C.L.C.), and Cardiothoracic Surgery (M.G.), The Ohio State University and Nationwide Children’s Hospital, Columbus, Ohio. Presented at: Update on Pediatric Cardiovascular Disease February 6-10, 2008, Scottsdale, AZ. Reprint requests: Clifford Cua, MD, Columbus Children’s Hospital, 700 Children’s Drive, Columbus, OH 43205-2696 (E-mail: [email protected]). 0894-7317/$34.00 Copyright 2008 by the American Society of Echocardiography. doi:10.1016/j.echo.2008.08.005
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traditional surgical options.2,3 Although the physiology is different, the goals of the palliation are the same as the traditional surgical palliation, which are to control pulmonary blood flow, provide reliable systemic cardiac output, and create an unrestrictive interatrial communication. After the comprehensive stage II surgery, which consists of pulmonary artery debanding, stent removal, arch augmentation with anastomosis of the main pulmonary artery to the ascending aorta, atrial septectomy, and bidirectional Glenn anastomosis, the physiology of patients undergoing the hybrid palliation is equivalent to those who have undergone a more traditional pathway through the bidirectional Glenn procedure (anastomosis of the superior vena cava to the pulmonary artery). Although echocardiographic findings have been described for patients who have undergone the classic Norwood procedure4-6 (atrial septectomy, anastomosis of the main pulmonary artery to the ascending aorta, aortic arch augmentation, and placement of a shunt from the innominate artery to the right pulmonary artery [RPA] to
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supply pulmonary blood flow) or the modified Norwood procedure7 (pulmonary blood flow supplied via a right ventricular to pulmonary artery conduit instead of a shunt), and subsequently the bidirectional Glenn operation8,9 and Fontan procedure10,11 (anastomosis of the inferior vena cava to the pulmonary artery), no data exist for those undergoing hybrid palliation. There are different physiologic issues that must be followed echocardiographically for patients undergoing the hybrid palliation versus those who undergo a more traditional pathway. The goal of this study was to describe the echocardiographic changes during the interstage (IS) period, defined as the time from hospital discharge after hybrid palliation to hospitalization for the comprehensive stage II operation, and to determine whether certain echocardiographic parameters may predict morbidity and mortality. MATERIALS AND METHODS Patient Selection This study was approved by the Institutional Review Board of Nationwide Children’s Hospital. Inclusion criteria included patients with HLHS, defined as aortic atresia/mitral atresia, aortic atresia/ mitral stenosis, or aortic stenosis/mitral stenosis, who underwent hybrid palliation and were discharged from the hospital. Patients were excluded if they (1) had an anatomic diagnosis different from those stated above, (2) were followed at another institution during the IS period, or (3) had not undergone their comprehensive stage II operation at the time of the analysis. A retrospective chart review was performed on all patients who met the inclusion criteria. Baseline data consisting of anatomic diagnosis, gender, age, and weight at the time of the hybrid procedure were recorded. Interventional procedures performed before the hybrid procedure and any additional IS cardiac procedures were documented. The age and weight of the patient at the comprehensive stage II were also recorded. Echocardiography All cardiac ultrasound examinations were performed at the Nationwide Children’s Hospital as part of routine clinical care. Examinations included standard transthoracic 2-dimensional echocardiography and pulsed, continuous wave, and color Doppler using variable frequency transducers. The studies were performed using various ultrasound systems (Sonos 5500 and iE33, Philips Medical Systems, Andover, MA; Vivid 7, GE Medical, Milwaukee, WI; Sequoia C256, Siemens, Mountain View, CA). Echocardiograms post-hybrid palliation before hospital discharge, before and after an IS intervention, and before the comprehensive stage II procedure were reviewed. The echocardiograms evaluated post-hybrid palliation were usually within 2 to 3 weeks after the procedure, and the pre-comprehensive stage II was also within 2 to 3 weeks before the operation. Offline analysis of the distal RPA and left pulmonary artery (LPA) (Figure 1) peak velocities (m/s), slope (cm/s2), VTI (cm), pressure halftime (P1/2) (ms), PI (peak systolic velocity-diastolic velocity)/mean velocity, and systolic/diastolic (S/D) ratio of the waveforms were recorded (Figure 2) in the parasternal short-axis view. ASD mean gradient (mm Hg) in the subcostal view (Figure 3), ductus arteriosus peak velocity (m/s) (Figure 4), and retro-aortic arch peak velocity (m/s) (Figure 5) in the high parasternal view were documented. The highest velocity or gradient that was imaged was recorded. Qualitative assessment of TR and right ventricular function was also documented. TR was graded as severe if there was systolic flow reversal in the inferior vena cava or hepatic vein, moderate if there
Figure 1 High parasternal short-axis view of the typical branch pulmonary arteries and ductal stent image. LPA, Left pulmonary artery; MPA, main pulmonary artery; PDA, patent ductus arteriosus; RPA, right pulmonary artery.
Figure 2 Typical Doppler pattern of the branch pulmonary artery velocity wave form and the various measurements performed. PHT, Pressure halftime; VTI, velocity time integral. was right atrial enlargement without flow reversal, mild if there was a regurgitant jet present without right atrial dilation, and trace/none if there was trivial or no jet present. Regurgitation and function were graded as 1 ⫽ normal/trace, 2 ⫽ mild, 3 ⫽ moderate, and 4 ⫽ severe for statistical purposes. Statistical Analysis The data are described with means, standard deviations, and percentages. Exploratory hypotheses were tested with chi-square and t tests. Stepwise logistic regression was used to identify any multiple sets of relatively independent variables. RESULTS Study Population Between July of 2002 and December of 2006, 35 patients with the diagnosis of HLHS underwent hybrid palliation and were discharged
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Figure 3 Subcostal view of the atrial septum documenting aliasing across the defect. Doppler interrogation would be performed in this view to obtain the mean gradient across the septum. from the hospital. Two patients were followed at another institution, and 3 patients were awaiting their comprehensive stage II procedure. Therefore, the cohort for this study consists of 30 patients. The age at hybrid palliation was 11.3 ⫾ 15.8 days (median 8 days, range 2-15 days), with 1 patient undergoing the hybrid palliation at 93 days as a rescue procedure. The weight was 3.0 ⫾ 0.6 kg (median 3.0 kg, range 1.4-4.5 kg). Four patients weighed less than 2.5 kg at the time of the hybrid palliation. Twenty-four (80%) of the patients were male. Sixteen patients (53%) had aortic atresia/mitral atresia, 4 patients (13%) had aortic atresia/mitral stenosis, and 10 patients (33%) had aortic stenosis/mitral stenosis. Four patients had a highly restrictive ASD that required urgent balloon atrial septostomy before undergoing hybrid palliation. Fourteen patients (47%) underwent a total of 18 separate cardiac catheterization procedures with a total of 22 interventions performed at the atrial septum, ductus arteriosus, or distal aortic arch during the IS period. Six additional stents were placed in the ductus arteriosus, 7 repeat balloon atrial septostomies were performed, 3 dilations of the ductus arteriosus stent were performed, 3 stents were placed in the distal arch, 1 stent was placed in the atrial septum, 1 dilation of the descending aorta was performed, and 1 dilation of the left pulmonary vein was performed. Two patients required reoperation: one for progressive pulmonary vein stenosis and one for a loose pulmonary artery band. There were 2 IS deaths. The weight at the comprehensive stage II procedure was 5.6 ⫾ 1.1 kg, and the age was 167.4 ⫾ 60.8 days.
Figure 4 (A) High parasternal image where highest velocity is usually obtained across the ductus arteriosus stent. (B) Continuous wave Doppler across a stenotic ductus arteriosus stent. CW, Continuous wave; PDA, patent ductus arteriosus.
Echocardiographic Data By comparing the post-hybrid echocardiogram with the pre-comprehensive stage II echocardiogram in the patients who did not undergo any IS intervention, there were significant differences in a number of the Doppler variables (Table 1). Significant interval changes in the flow characteristics in the LPA and RPA, with increases in the peak velocities, VTI, P1/2, and S/D ratios, and a decrease in PI, were documented. The LPA and RPA slope, however, did not change significantly. There were significant increases in the ductus arteriosus velocity, ASD mean gradient, and retro-aortic arch peak velocity during this time period.
When examining the echocardiographic data on the subset of patients who underwent an IS intervention (Table 2), there were similar increases in the LPA and RPA peak velocities and VTI, ductus arteriosus flow velocity, and retro-aortic arch peak velocity. In addition, there were significant changes in the ASD gradient, LPA slope, degree of TR, and right ventricular function between the post-hybrid echocardiogram and the echocardiogram before the intervention. By analyzing each of the different interventions separately, there were no significant differences in any of the parameters between the post-hybrid and pre-intervention echocardiograms at the distal aortic
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Table 1 Post-hybrid echocardiogram versus pre-comprehensive stage II procedure echocardiogram in patients who had no interstage intervention Post-hybrid echocardiogram
LPA velocity (m/s) RPA velocity (m/s) LPA VTI (cm) RPA VTI (cm) RPA p1/2 (ms) LPA PI RPA PI RPA S/D ASD gradient (mm Hg) DA velocity (m/s) Retro-aortic arch (m/s)
3.58 3.54 98.04 103.43 121.44 1.12 1.03 3.60 1.39 1.61 1.71
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.80 0.81 32.12 32.05 26.32 0.20 0.32 1.90 1.08 0.47 0.67
Pre-stage II echocardiogram
4.38 4.06 137.15 131.49 142.48 0.92 0.79 2.33 3.21 2.82 2.56
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.59 0.44 36.31 27.60 24.51 0.32 0.18 0.44 2.35 0.44 1.02
P
.004 .037 .009 .022 .029 .031 .022 .025 .029 ⬍.001 .035
ASD, Atrial septal defect; LPA, left pulmonary artery; NS, not significant; DA, ductus arteriosus; PI, pulsatility index; RPA, right pulmonary artery; VTI, velocity time integral; p1/2, pressure halftime.
Table 2 Post-hybrid echocardiogram versus pre-intervention echocardiogram Post-hybrid echocardiogram
LPA velocity (m/s) RPA velocity (m/s) LPA slope (cm/s2) RPA slope (cm/s2) LPA VTI (cm) RPA VTI (cm) LPA p1/2 (ms) RPA p1/2 (ms) LPA S/D RPA S/D LPA PI RPA PI ASD gradient (mm Hg) DA velocity (m/s) Retro-aortic arch (m/s) TR RV function
3.48 3.44 920.10 866.01 90.80 99.07 107.29 115.95 3.85 3.24 1.09 1.00 2.14 1.84 1.76 1.22 1.06
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
Pre-intervention echocardiogram
P
0.71 3.97 ⫾ 0.82 .005 0.66 3.89 ⫾ 0.62 .008 298.74 1081.22 ⫾ 405.55 .041 216.12 975.36 ⫾ 340.29 NS 28.43 115.07 ⫾ 41.78 .002 24.02 117.56 ⫾ 36.11 .015 25.11 118.11 ⫾ 43.65 NS 22.44 125.91 ⫾ 37.56 NS 2.10 3.60 ⫾ 1.94 NS 1.35 3.39 ⫾ 2.15 NS 0.21 1.11 ⫾ 0.27 NS 0.17 1.11 ⫾ 0.33 NS 1.52 4.91 ⫾ 4.33 .001 0.44 2.76 ⫾ 0.57 ⬍.001 0.47 2.34 ⫾ 0.81 .002 0.49 1.61 ⫾ 0.90 .017 0.23 1.30 ⫾ 0.76 .02
ASD, Atrial septal defect; LPA, left pulmonary artery; NS, not significant, DA, ductus arteriosus; PI, pulsatility index; RPA, right pulmonary artery; RV, right ventricle; TR, tricuspid regurgitation; VTI, velocity time integral; p1/2, pressure halftime.
Figure 5 (A) High parasternal image where the retro-coarctation is best visualized. (B) Continuous wave Doppler across a stenotic retrograde aorta. CW, Continuous wave; PDA, patent ductus arteriosus.
arch, although there was a trend for increased TR (1.50 ⫾ 0.58 vs 3.00 ⫾ 0.82, P ⫽ .058). There was a significant increase in ductus arteriosus velocity on the echocardiograms for those undergoing a ductus arteriosus intervention (1.98 ⫾ 0.29 m/s vs 2.95 ⫾ 0.69 m/s, P ⫽ .003). There was a significant increase in the RPA slope (857.18 ⫾ 250.85 cm/s2 vs 1134.95 ⫾ 317.95 cm/s2, P ⫽ .044), but not in the LPA slope (933.411 ⫾ 276.18 cm/s2 vs 1106.71 ⫾ 322.24 cm/s2, P ⫽ .25), for those undergoing an intervention at the atrial septum. The ASD gradient (2.74 ⫾ 1.69 mm Hg vs 10.13 ⫾ 4.93 mm Hg,
P ⫽ .005) and TR (1.00 ⫾ 0.00 vs 1.71 ⫾ 0.76, P ⫽ .047) also significantly increased for these patients. There were significant differences in LPA and RPA VTI, p1/2, and S/D, and RPA slope, ASD gradient, ductus arteriosus gradient, and TR pre- and post-intervention (Table 3) for those requiring a procedure. A post-hybrid echocardiogram ASD mean gradient (P ⫽ .012) greater than 4.9 mm Hg or a ductus arteriosus peak velocity (P ⫽ .002) greater than 1.7 m/s predicted an IS intervention. However, there was no specific echocardiographic parameter that predicted a specific catheterization intervention. No echocardiographic parameter predicted comprehensive stage II mortality, although right ventricular function tended to predict death (P ⫽ .085).
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Table 3 Pre-intervention echocardiogram versus post-intervention echocardiogram Pre-intervention
LPA velocity (m/s) RPA velocity (m/s) LPA slope (cm/s2) RPA slope (cm/s2) LPA VTI (cm) RPA VTI (cm) LPA p1/2 (ms) RPA p1/2 (ms) LPA S/D RPA S/D LPA PI RPA PI ASD gradient (mm Hg) DA velocity (m/s) Retro-aortic arch (m/s) TR RV function
3.79 3.75 1152.84 1099.01 103.89 95.28 105.76 110.76 3.82 4.28 1.11 1.14 6.82 2.71 2.20 1.89 1.45
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.81 0.74 440.51 405.45 37.05 16.72 36.54 39.70 1.71 2.64 0.33 0.33 5.41 0.66 0.65 0.94 0.89
Post-intervention
P
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
NS NS NS .013 .011 .03 .038 .008 .012 .033 NS NS .003 .021 NS .031 NS
4.10 3.72 975.72 852.79 128.32 116.83 124.89 136.00 3.06 3.04 1.04 1.07 1.11 2.37 2.23 1.53 1.15
0.86 0.69 212.26 246.81 41.63 30.10 26.50 39.14 0.74 1.29 0.22 0.43 0.33 0.62 0.77 0.70 0.37
ASD, Atrial septal defect; LPA, left pulmonary artery; NS, not significant; DA, ductus arteriosus; PI, pulsatility index; RPA, right pulmonary artery; RV, right ventricle; TR, tricuspid regurgitation; VTI, velocity time integral; p1/2, pressure halftime.
DISCUSSION Hybrid palliation for newborns with HLHS is a relatively new technique for this population. The surgical and catheterization techniques have been described,1,2 but echocardiographic data have not been previously presented. Specifically, the echocardiographic parameters during the IS period, when the physiology of patients undergoing this procedure is different in comparison with those undergoing a classic or modified Norwood procedure, have not been previously delineated. This study shows that specific echocardiographic parameters change in a predictable manner during this time period and that variations from these changes may determine the clinical course. The post-hybrid echocardiogram ASD mean gradient and peak ductus arteriosus velocity were useful in predicting whether a patient would later require an IS intervention. No specific echocardiographic parameter predicted a certain catheterization procedure, but this may be because some patients had multiple procedures performed at a single catheterization. We no longer routinely perform a pre-comprehensive stage II catheterization, so the decision to perform an interventional catheterization is based on both clinical and echocardiographic data.2 Repeat balloon septostomy was performed if the echocardiographic mean gradient was 8 mm Hg or greater. The decision to intervene at the ductal or arch level is more complicated. Interventions at the ductal or arch level were performed if there were increasing gradients in these areas and worsening TR or right ventricular function. Clinical aspects, such as patient’s feeding pattern, weight gain, and electrocardiogram changes, also affected the decision to perform an intervention at the duct/arch. The complex changes in physiology with multiple procedures performed and the various clinical parameters used to guide the decision to intervene would make exact predictions difficult from the post-hybrid echocardiogram. Changes among the post-hybrid echocardiogram, pre-intervention echocardiogram, and post-intervention echocardiogram can be explained by changes in resistance distal to the pulmonary artery bands or increasing afterload. Restriction of flow across the atrial septum
Figure 6 (A) RPA Doppler interrogation in a patient with a restrictive atrial septum. Doppler pattern shows steep slope and low diastolic velocity. (B) RPA Doppler pattern after atrial balloon septostomy in the same patient. Notice the increase in diastolic velocity. Subsequent measurements documented increase in VTI, decrease in slope parameter, increase in pressure halftime, and decrease in S/D ratio. RPA, Right pulmonary artery; ¡, loss of forward during diastole; S/D, systolic/diastolic velocity.
and pulmonary vein obstruction can both result in increased diastolic pressures and thus decreased pulmonary blood flow. As a result, Doppler velocities across the bands will equilibrate quicker, as evidenced by the steeper slope seen in the pulmonary arteries. Although not statistically significant, a decrease in the systolic and diastolic velocities and an increase in PI have been noted as the ASD gradient increases. In severe restriction, diastolic flow across the bands can become minimal or nonexistent. When the restriction has been relieved, the pulmonary blood flow improves, the diastolic blood pressures decrease distal to the pulmonary artery bands, and the slope of the pulmonary waveforms becomes less steep and the PI decreases (Figure 6).
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Similarly, increasing afterload, either in the form of increasing stenosis across the ductal stent or retro-aortic arch, would result in decreased coronary perfusion, especially in patients with aortic atresia and thus no antegrade aortic flow. Coronary hypoperfusion would result in ventricular dysfunction, ventricular dilation, and TR. A stenotic ductus arteriosus stent will also increase systolic and diastolic ventricular pressures resulting from increased afterload and secondary hypertrophy of the single ventricle. This is consistent with the findings that TR and right ventricular dysfunction qualitatively increased compared with the hospital discharge study in patients requiring an intervention. Conversely, when the obstruction was relieved, the echocardiographic parameters postintervention corresponded to the values just before the comprehensive stage II procedure. Again, qualitatively, TR and ventricular function improved post-intervention. A more rapid or greater change in ductus arteriosus or retro-aortic arch flow velocities may signal intimal in-growth through the cells of the ductus arteriosus stent. In some cases this may be difficult to discern from the typical increases seen with growth, and clinical correlation is essential to determine further treatment plans. The echocardiogram before the comprehensive stage II procedure also was not predictive of mortality, although decreased right ventricular function tended to predict death. The lack of predictive power may be due to the small numbers studied, but it may also be due to the qualitative manner of grading right ventricular function. Because of the complex geometry of the right ventricle, no universal quantitative echocardiographic parameter has been agreed on. Newer techniques, such as 3-dimensional echocardiography, tissue Doppler velocities, strain, or strain rate, may be more sensitive markers for right ventricular function and thus be more predictive for clinical course.12-14 The echocardiographic changes seen between the post-hybrid and pre-comprehensive stage II procedure are likely due to multiple factors, including patient growth, fixed dimensions of anatomic structures such as the pulmonary artery bands and ductus arteriosus stent, and decreasing pulmonary vascular resistance. All 3 factors can explain the increases in peak pulmonary artery velocities and VTI measurements across the pulmonary artery bands and the decrease in PI. The increase in ductus arteriosus velocity can also be attributed to the fixed nature of the ductus arteriosus stent in the setting of a growing infant. Even patients who did not undergo an intervention had significant changes in parameters, and this may be the natural history as described above; thus, post-hybrid values cannot be considered a stagnant value. Although not examined in this study, growth appears to change the orientation of the distal arch in relation to the ductus, resulting in a more acute takeoff and altered flow dynamics resulting in more flow acceleration over time.15,16
LIMITATIONS The limitations of this study include its retrospective nature and the small numbers studied, although it is the largest study to date examining echocardiographic parameters in this complex patient population. Right ventricular function was qualitatively graded, so although it tended to predict comprehensive stage II mortality, no quantitative measurement at this time is available to predict death. Patients may also have had multiple interventions performed at a single cardiac catheterization, so complex physiologic interactions may not be totally explained by the pre- and post-echocardiographic findings.
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CONCLUSIONS Consistent and predictable changes in Doppler parameters were observed in patients with HLHS after hybrid palliation. Careful monitoring of these echocardiographic parameters with clinical correlation can help predict the IS course and the need for interventional therapy for this patient population. Close attention to changes in TR and right ventricular function is warranted. Further studies are needed to determine whether newer echocardiographic modalities of ventricular systolic and diastolic function may be more useful in identifying potential hemodynamic issues earlier and alter IS management and outcome for this patient population.
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13. Friedberg MK, Silverman NH. The systolic to diastolic duration ratio in children with hypoplastic left heart syndrome: a novel Doppler index of right ventricular function. J Am Soc Echocardiogr 2007;20:749-55. 14. Christensen D, Cardis B, Mahle W, Lewis R, Huckaby J, Favaloro-Sabatier J, et al. Pre- and postoperative quantitation of right ventricular tissue Doppler velocities in infants with hypoplastic left heart syndrome. Echocardiography 2006;23:303-7.
15. Boucek MM, Mashburn C, Kunz E, Chan KC. Ductal anatomy: a determinant of successful stenting in hypoplastic left heart syndrome. Pediatr Cardiol 2005;26:200-5. 16. Lemler MS, Zellers TM, Harris KA, Ramaciotti C. Coarctation index: identification of recurrent coarctation in infants with hypoplastic left heart syndrome after the Norwood procedure. Am J Cardiol 2000; 86:697-9, A9.
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